Going down the big horns is a real test of your breaks.
Places to see on the way out are Custer State Park in the South Dakota / Black Hills. You will see plenty of wild animals in the park and campground. If you stay their 2 or 3 days you can take in the Black Hills sites of Mount Rushmore, Wind Cave, Needles Highway and Spearfish Canyon.
Also about 45 minutes east of the Black Hills is the Bad Lands National Park.
About 1.5 hours west of the Black Hills is Bear Butte in Wyoming that is also interesting. Their is a KOA campground just outside of Bear Butte also.